Addition of acid to halt polyurethane producing reaction



United States PatentCfi 6 Claims; (Cl; 260-775 This invention relatesto thekproduotioni of. polymers and relates moreparticularlytoa processtor' the production of polymers.ofimproved thermal stability. .1 I

An importantfobject ofrthisinventionnis .to providea N.Q;J.,eassignor to Celanese- .New York, N. Y., a corpo-v novel process torlthelproduction ofv polymersiofsimproved lh6Ill'l3lrStflbllil2Y...-

A furthenobjct ,ofthislinvention-is tqprovideIa proc-w ess :for. .the, production .of 7 thermal stability by; the reaction of va bis-chloroformate. and apolyamineinia.heferogeneousrreaction system.

Other objects of this invention will. be -apparent from" the following .detaileddescripti'on and claims.

It has previously]beenaproposed to produce. poly-Q urethanes by the. polymerizationeof a bis-chloroformate and a-polyamine. According to one processthat has been suggested for carrying out this polymerization- -in-a heterogeneous. reaction medium, thereare mixed together, with vigorous stirring. and preferably .in thepresencenof; an emulsifying agent,-an aqueoussolution of a polyamineand a Water-immiscible.organicQsolventsolution of a bischloroformatel There is alsc xaddedto the. polymerization mixture an .acid. binding 1' agent I .to react. with vthe hydroa chloric acid that is liberated-as-thepolymerization proa ceedsa The polymer precipitatesefrom the reaction mix ture as it is formed. toproduce. a slurry. As set forth i111" Jones :et al. applicationSt-NoQ177,763, filed December 3, 1951, now Patent .No; 2,660,574, there maybe present initiallyin the polymerization. mixturea sufiicientquantity of an acid material. to prevent. thereaction-from; proceeding, and thetpolymerization may. be caused to takes place by. introducing-an alkaline material into thepoly merization mixture. i

It has now been discoveredthat polyurethanes -ofim-'=-- proved thermal s tabilitymay. be prepared: by a the --fore'- going processes if the--polymerization is interrupted -be-- fore ithas gone.to.completion. -Apparently, in carrying,- out the polymerization, the polymerproduced duringthewfinal stages-of= the reaction .isoflowermolecular weight e than the polymer produced. during the ear-ly stages of the reaction and will causea noticeableimpairment the thermal stability of the-gfinalv-productau Byrinterrupting. the polymerization before. it has progressed to completionit is possible substantiallytoprevent the formation of'the t low molecular weight. polymer. that is normally- "formed; a during the final stages .ofthereactionand thereby to improve the. thermal stability' of a the product.--=

The interruption of thepolymerization may be effected in a number of diflierent ways. In smallscale operatiortg the polymerization may be 1 interrupted-rapidly by filtering thereaction mixture or.otherwise treatingthe'sameso as to separatephysically.thealready formed polymerw from the reaction mixture.containingunreacted materials. P This method of interrupting the polymerization is not, however, generally-applicable to large scale operations, because of the ditficulties involved-in therapidfiltr-ation: of large evolumes of materiaL- Another and more genpolyurethanes of improved 255C. or 35 erally useful method ofainterrupting the polymerization is .toacidify thereaction mixture by adding 'an acid reacting material thereto.

basiccriterion-for these methods being that they will cause a reaction to take place 1east-one-of the reactants the reactive amino' groups of the polyamine maybe destroyed by-reaction with nitrous acid to interrupt the polymerization:

Products of improved intrinsic viscosity and good thermal stability may be obtained by interrupting the polymerizationbefore it has progressed to a point where morethan about 95% of the amount'of polymer hasbeen formed which would be obtained if the polymerization were allowed to go to obtained when'the polymerization is interrupted before-it hasyprogressed'to a pointzwhere more than about of -this amount of polymer has been formed. In general;

the-interruption of the polymerization may be-efiected within an interval of it has-commenced, polymerizatiomis carried out very slowly or withunusual rapidity,

' invention are characterized by'a higher-me1ting point and a higheraint-rinsicviscosity than polymers produced --by prior processes wherein the polymerizatiom is permitted to go'isubstantially to completion?- They also exhibit a and the like; or' ing"operations.--

The processes of this invention is applicable to the--pro-* ductionaof polyurethanes by a applicableto the production of polyurethanes by a con-- 1 batch-process; It is also tinuous process as disclosed, forexample, in Swerdloff et al.,- 'app lication S. N0. 250,18-7, filed October-'6, 1951,- nowPatent'No. 2,658,886. As set-forth in that applica tion, the polyurethane is prepared by introducing 'continuously -into a reaction zone an aqueous solutio'nof a polyamine and an organic solvent solution of a bis-chloro--- formate, and effecting a po'lymerizationreaction in said zone by continuously and stronglyagitating; the mixture therein. -'Theslurry-formed as the reactionproceeds is withdrawn continuously from the reaction zone at 'a volu'met-ricrate equal'to the volumetric ratethe solutionsare introduced therein. To interrupt the polymerization at "a predetermined point, the-polymer slurry 'may; be withdrawn continuously this r-pointand the slurry may be -filtered or otherwise reacted material. Alternatively;

be int'errupted by acidifying thepolymer'slurry'or otherwisechemieally treating the same to destroy or tie up at least: one of the reactants.

Thetemperature of the solution undergoing polymeri zatiorris advantageously maintained at fromabout 0 to yield of polymer However, lower temperatures 'C. or even lower may also be em-' suitable antifreeze I agent' such as -C. to obtain the maximum ofhigh; molecular weight. down to about 10 ployed byadding a methanol ethylene glycoLglycerine, acetone or dioxane to the aqueous polyamine solution and forming the bis ,chloroformatesolution with an organic solvent having a freezing'pointbelowthe temperature at'which the poly- Higher temperatures may also out the polymerization, but are somevt hatw'less"desirable in that they *resiilt in a lower merizationis carried out. be employed for carrying Patented-Julyt23, 1957' Other chemical methods may also-be-employed for interruptingthe'polyinerization, the

with the reactive groups 'of 'at to prevent said reactant from entering into the polymerization-reaction. For example;

completion, but the best results are betweenabout 2 and 8 minutes afteralthough in certain cases where the a a longer-or shorterperiod, respectively, may be necessary. The polymers produced by the process-of this at which" I from the reaction zonebefore the polymerization has progressed beyond" yield of polymer having a lower and less uniform molecular weight.

In forming the organic solvent solution of the bis- 7 agent.

chloroformate, there may be employed a wide variety of water-immiscible solvents. Suitable solvents include benzene, toluene, xylene, chloroform, carbon tetrachloride, octane, naphthene, and the hydrocarbon mixture of aromatics, paraflins and naphthalenes sold under the name Varsol. Aromatic solvents, particularly toluene, are preferred for this purpose since they result in a maximum yield of polymer of the desired molecular weight.

During the polymerization reaction, hydrochloric acid is liberated and reacts with the alkaline agent that is introduced into the reaction zone togetherwith the polyamine and the bischloro'formate. 7 agent is employed in excess of that required exactly to neutralize all of the hydrochloric acid'formed. Depending upon the specific alkaline agent, the optimum results with regardtoyield are obtained with a molar excess of up to about 100%. Suitable alkaline agents that maybe employed, in addition to sodium hydroxide and sodium carbonate, are an excess of the polyamine, itself, the soluble Preferably, the alkaline alkalimetal or alkaline earth metal oxides, hydroxides,

and carbonates, such as potassium hydroxide, barium hydroxide, di'sodiumphosphate and trisodium phosphate, quaternary ammonium bases and the like. The alkaline agent may be dissolved in the aqueous polyamine' solution before the in the form of a separate solution.

The process of the present invention is particularly advantageous in that it permits the polymerization to be carried out at a high pH, i. e., at a pH of above 10 or between 12 and 13. Despite the extremely high alkalinity of these "polymerization mixtures, no degradation of the polymer takes place as with prior processes, apparently because of the interruption of the polymerization after it has progressed to the desired extent, i. e., prior to completion.

Various types of emulsifying agents may be introduced into the reaction zone, either in solution with one of the latter is introduced into the reaction zone, 'or it may be introduced into the reaction zone melting point.

reactants or separately, to assist in effecting a uniform and rapid emulsification of the reactant solutions. Examples of suitable emulsifying agents are ethylene oxide condensates with long chain fatty alcohols, esters of sodium sulfosuccinic acid such as the dioctyl ester, long chain fatty acid esters of polyethylene glycol, ethylene oxide conderisates with castor oil, long chain monoglycerides, alkyl aryl polyether alcohols, e. g. the reaction product of ethylene oxide and xylenol, sorbitan monolaurate, the

condensation product of sorbitan monolaurate with ethylene oxide, mono-or polyalkyl naphthalene sulfonates,

sulfates offatty acid monoglycerides or the glycol esters of long chain fatty acids. It is important, for the-production ofipolymers of good color, that the emulsifying agent be as free as possible of colored bodies, as the polymer tends to scavenge colored bodies from the emulsifying agent and the reaction mixture. The most advantageous results are obtained, however, by employing emulsifying agents comprising the sodium salts of sulfated long chain alcohols, such as sodium lauryl sulfate,

The amount of emulsifying agent employed is preferably from about 4.5 to'l0.5 grams/gram mole of reactants on a 100% strength basis.

Examples of diamines which may be employed in forming polyurethanes in accordance with the novel polymerization process of our invention are ethylene diamine, trimethylene diamine, tetramethylene diamine, pentamethylene diamine, hexamethylene diamine, ortho-, metaor para-phenylene diamine, cyclohexylene diamine and nuclearly substituted phenylene diamines and nuclearly substituted cyclohexylene diamines. N-substituted diamines which contain a free amino hydrogen on each amino group arealso suitable.

Other diamines which may also be employed are, for example, u,w-di-(3-aminopropoxy)-alkanes, such as 1,4 di(3aminopropoxy) -butane, bis-(w-amino alkyl) ethers such as 3,3'-diamino-di-propyl ether, 4,4'-diamino-dicyclohexyl methane, bis-(w-amino-alkyl) sulfides such as 2,2" diamino-diethyl-sulfide, 1,2-,' l,3'- 1-4-a,a'-diamino xylene or other w,w'-diamine-dialkyl benzene, diamino-naphtha lene, diamino-biphenyl, w,w -diamiuo dialkyl biphenyls, wamino-alkylanilines, w-aminoralkylcyclohexylamines, bis- (w-amino-alkoxy)'-benzene, bis-(w-arnino-alkoxy)-cyclohexane; 4,4'ediamino-dicyclohexyl sulfones, w,w'-sulfonylbis-alkyl amines, diamine-diphenyl sulfones, diamino-benzophenones and N,N-bis-(w-amino-alkyl)-d,walkane disulfonamides. Amines containing more than two reactive amino groups, either primary or secondary, such as diethylene triamine or triethylene tetramine, for example, yield branch chain polyurethanes. Such polymers, if they contain moderately branched chains, are of relatively low If the chains are highly branched the polymers approach and may even reach substantial infusibility.

Th'e bis-chloroformates which are reacted with the above mentioned diamines may be obtained by reacting phosgene, i. e. carbonyl chloride, with a diol. The bischloroformates of diols such as ethylene glycol, trimethylene glycol and 1,4-butancdiol, for example, are suitable. Higher glycols wherein the alkylene chain contains a greater number of carbon atoms and may be a straight chain or a branched chain are also satisfactory. Examples of other diols whose bis-chloroformates may be employed arew,w-dihydroxyl-dialkyl ethers, w,w'-dihydroxy-dialkyl thioethers, bis-glycol or diglycol esters of straight chain or branched'chain aliphatic dicarboxylic acids such as the bis-ethylene glycol ester of succinic acid, the bis-diethylene glycol ester of succinic acid, the bisethylene glycol ester of glutaric acid, the bis-ethylene glycol ester of adipic acid, the bis-ethylene glycol ester of pimelic acid, the bis-ethylene glycol ester of suberic acid, azelaic acid or sebacic acid, the diol, dimer or trimer esters obtained by the conversion of an excess of an aliphatic glycol with a dicarboxylic acid of the several aliphatic dicarboxylic acids mentioned above, w,w'-dl-hydroxy-dialkyl ethers of hydroquinone, w,w'-di-hydroxydialkylethers of di-hydroxy cyclohexane, w,w'-sulfonyl bis-alkanols, i. e. bis-(w-hydroxyalkyl-sulfones), N, N'-

sodium octyl sulfate, sodium oleyl sulfate and the like.

Other emulsifying agents, that may be employed include the sodium salt of an N-substituted amino-ethane-sulfonic acid, i. e. an N-substituted taurine. the nitrogen may include both alkyl groups, such as methyl, ethyl, propyl, butyl, amyl, hexyl, heptyl, octyl, decyl,undecyl, dodecyl, etc., and acidyl groups. The acidyl group, when present, is preferably the acidyl group of a long chain saturated or unsaturated aliphatic acid containing six to eighteen carbon atoms. Examples of The substituents on said acids are lauric,v oleic, "ricinoleic, linoleic, caproic,

pimelic, heptylic, undecylic'and stearic acid. Good results are achieved by employing the sodium salt of N-butyl,

N-lauroyl-fl-amino-ethane sulfonic acid as the emulsifying (w-hydroxyl-alkyl)-dicarboxyamides such as N, N-(p,;s'- dihydroxy-diethyl) adipamide, 'cycloaliphatic glycols as cyclohexylene glycol, 'dihydroxy tetrahydrofurane, hydroxy hydroxymethyl furane, hydroxy hydroxymethyltetrahydrofurane, and dihydroxy-oxathiane dioxide.

Thus, the polyurethane may contain an'alkylene linkage of two, three, 'four, five or more carbon atoms alternating with an alkylene linkage of two, three, four, five or more carbon atoms. For ready identification the alkylene polyurethanes may be identified as, 2,4-, 3,4 4,4 5,6-, 6,6-, etc. polyurethanes, the former numeral referring to the carbon chain length of the diamine employed while the latter refers to the carbon chain length of. the bis-chloroformate. I Mixed polyurethanes containing any type of intermediate linkage or grouping as brought out above may also be formed by employing any of the diamines and bis-chloroformate'of the diols mentioned or a mixture asun er of two or moredflfr'entdiminesor twoorinore difweightofpolymer'or87.0%of'theoryi This"polymer ferent bis-chloroformates. in"'thiscaseis'foundtohavea meltingp int of 204 C.

Pigmented polyurethanes maybe readily obtained by and an intrinsic viscosity of 1.22.

introducing into the polymerization mixture a slurry or his to beunderstood" that thefor'eg'oing detailed d dispersion of a suitable pigment such as titanium dioxide, 5 scriptionis 'given'rnerely by way of illustration and that" Franconia blue, Opaline "green," or carbon black. many variations may be made therein without departing Aci materials that may be employed for interrupting rom e p' fi y invention;

the polymerization reaction by acidifying the L reaction H vi gfl y inventiom'wha'tl desirto Secure mixture include, for example, hydrochloric acid, sulfuric by Letters Patentis:

acid and phosphoric acid'. Suflicient acid material should 10 Pr'hc'ess' folithe 'prodlietihfl f polyurethanes; which be added to the polymerization mixture to reduce its pH Comprises "fofml'h'glia heterhgeheous mixture vcontainingto less than about 6 or preferably less than about to ill Q p poly min free'from i'eativ grdiip'S ot er insure that-nofurther polymerizati'on'will take place. Ihah h ps 311d at leasf'hne hydrogen 'athm The following examples are given to" 'illustrate thi's attahea eachwlliffhgeli'vathhluand ifl'another P s invention further. a bis-chloroformate free from reactive groups other than Example I the chloroformate groups, effecting a polymerizatlon reacy is still proceeding and before the same reaches the point there is added a solution containing 66.7 parts by weight of butanediol bis-chloroformate, and 6 parts by weight of Igepon T in 1137 parts by weight of toluene. The mixby adding an acid to the mixture.

2. Process for the production of polyurethanes, which 5 comprises forming a heterogeneous mixture containing the chloroformate groups, eflfectin a 01 merization reacperature rises gradually from 2 to 12 C., the polymer g p y slurry is filtered rapidly to separate the polymer from bi hl of te to prod the unreacted monomers. After washing and drying,

of about 95% of the total theoretical ield of 01 mer ing point of 196 C. and an intrinsic viscosity of 0.97. being f m d X p y When the polymerization is repeated, using a stirring by a idifying t time of 19 minutes, there is obtained 58 parts by weight about of polymer or 94.8% of theory. The polymer in this 3 Process fo h 40 comprises forming a mixture of an aqueous solution of Example II groups and having at least one hydrogen atom attached A polymerization is carried out in the manner set forth in Example I and the polymerization is stopped at the point of about 95 of the total theoretical yield of polya polyamine free from reactive groups other than amino lfil e i z t c il eg zl i t z g rs fli y q roups and having at least one hydrogen atom attached c OI 301 Q 0 8 en P n P ere Is to each nitro en atom and an or anic solvent s lutio added a solution containing 66.7 parts by weight of g o n butanediol bis-chloroformate, and 6 parts by weight of Igepon T gel in 1,137 parts by weight of toluene. The

reaction Within said mixture between the polyamine and f 01 t1 ns 1s stirr d v 181 t r a g r l fl l gltgn tang :Sgfiiciem anioun t gg g5% P :;g 2 the bis-chloroformate to produce the polyurethane, and

I 4 minutes of stirring during whlch time the temperature pom about 95% of-the total th-eor-encal ylelfi of p O mer eing formed said polymerization reaction being rises gradually from 2 to 13 C., the polymerization is halted by acidifying the reach-0n mixture to a H f I stopped by the addition to the reaction mixture of suf- P o 688 After washing and drying, there is obtained 54.7 parts Process the pniducnon of polyurethanes .Which by weight of polymer or 79.4% of theory. The polymer compnses fommig Imxture of an l f q soluflon i is found to have a melting point of C and an 7 tetramethylene diamine and a water-1mm1sc1ble organic intrinsic viscosity of 150. solvent solution of butanediol bis-chloroformate, effecting When the polymerization is repeated Without acidificaa Polymenzatlon reacnon Within Said mixture between tion and using a stirring time of 4 minutes, followed the polyamine and the hischlomformate to Produce the by a 4 minute interval for separating the polymer from Polyurethane, and Causing the halting of said Polymerizw the reaction mixture, there is obtained 60.0 parts by tion reaction while it is still proceeding and before the same reaches the point of about 90% of the total theoretical yield of polymer by acidifying the reaction mixture to a pH of less than 5.

6. Process for the pro comprises forming a m ture of an aqueous solution of tetramethylene diamine and a water-immiscible organic solvent solution of butanediol bis-chloroformate, at a pH of between 12 and 13, efiecting a polymerization reaction within said mixture between the polyamine and the bis-chloroformate to produce the polyurethane, and causing the halting of said polymerization reaction while it is still proceeding and before the same reaches the point of about 90% of the total theoretical yield of polymer by acidifying the reaction mixture to a pH of less than 5.

duction of polyurethanes, which 8 References Cited in the file of this patent UNITED STATES PATENTS Jones e: 1. Nov. 24, 1953 Magat et a1. May 17, 1955.

FOREIGN PATENTS Great Britain Jan. 13, '1949 France Jan. 7, 1944 France May 7, 1945 OTHER REFERENCES 

1. PROCESS FOR THE PRODUCTION OF POLYURETHANES, WHICH COMPRISES FORMING A HETEROGENEOUS MIXTURE CONTAINING IN ONE PHASE A POLYAMINE FREE FROM REACTIVE GROUPS OTHER THAN AMINO GROUPS AND HAVING T LEAST ONE HYDROGEN ATOM ATTACHED TO EACH NITROGEN ATOM, AND IN ANOTHER PHASE A BIS-CHLOROFORMATE FREE FROM REACTIVE GROUPS OTHER THAN THE CHLORORFORMATE GROUPS, EFFECTING A POLYMERIZATION REACTION WITHIN SAID MIXTURE BETWEEN THE POLYAMINE AND THE BIS-CHLORAFORMATE TO PRODUCE THE POLYURETHANE, ANE CAUSING THE HALTING OF SAID POLYMERIZATION REACTION WHILE IT IS STILL PROCEEDING AND BEFORE THE SAME REACHES THE POINT OF ABOUT 95% OF THE TOTAL THERORETICAL YIELD OF POLYMER BEING FORMED, SAID POLYMERIZATION REACTION BEING HALTED BY ADDING AN ACID TO THE MIXTURE. 